CASE STUDY – Stanly County Deck
Girder Bridge
Tom Koch, PE - NC DOT, Structure Design Unit
Richard Potts, PE - Standard Concrete Products, Georgia Division
Mark Foster - Lee Construction Company of the Carolinas
Janos Gergely, PhD, PE - UNC Charlotte, Civil Engineering
Acknowledgements
•FHWA – Innovative Bridge Research and
Construction Program
•Brian Hanks, NCDOT
•Kevin Bailey, STV-Ralph Whitehead
•Reid Castrodale, Carolina Stalite
•LARSA Inc.
Presentation Outline
•Design and development (T. Koch)
•Deck girder fabrication (R. Potts)
•Bridge construction (M. Foster)
•Analysis and testing (J. Gergely)
Design and development


Tom Koch, PE
NCDOT, Structure Design Unit
Design and development
B-3700 Stanley County
Precast Deck Bulb Tee
110’ Single Span
Design and development
PVI= 17+15
El =485.10
L=820’
-1.34%
+7.00%
Design and development
•Deck Bulb tees - Come in standard shapes
•Used most extensively in Cold -weather states with a short
concrete pouring season (AK, WA, ND, SD, OR)
Design and development
Project Schedule
Original Design
•63” MBT’s , skew = 115 degrees
•Original Schedule Let Date : May 2005 , to be finished June
2006
•DBT Final Schedule -•Let: May 15 2005
•Availability: June 27, 2005
•Completion: November 1, 2005 (about a 4 month Construction
schedule)
Design and development
Design and development
6’-6
Deck Bulb Tee
32 -- 0.6”
Straight strands
Original Design: 63” MBT w/ 36 0.6”
strands
Design and development
Design and development
Design and development
Deck Bulb Tee Features

F’c initial = 5500 Psi

F’c final(28 day) = 9000 psi

Calcium Nitrite Corrosion Inhibitor

Concrete mix for girders was required to contain either Fly Ash,
Slag or Silica Fume

Diaphragms, connector plates, embedded angles were
galvanized

Final Girder Weight -- about 138 Kips
Design and development
Costs
Compared the cost to 60” Plate gdr. and a 63” MBT for a
similar one span bridge, 3600 - 4000 sq ft
•Sq. Ft Costs :
Plate gdr. = $84.56
63” MBT =
Type III DBT
=
$90.24
$118.48
Line item bid for Gdrs. = $301 K Total
Design and development
Lessons Learned
•Cracks in flanges due to integral abutment detailing -- details
will need to be improved if using for integrals
•DBT’s are an extremely efficient shape (high Length/Depth)
•DBT use is more ideal for crest vertical curves rather than sags
•Diamond grind rather than Asphalt overlay
•Construction schedule of 4 months could have been easily
reduced by at least a month to 6 weeks
•To speed acceleration even more, detail more precast elements substructure, rails
PRETOPPED TYPE III GIRDER
FABRICATION AND ERECTION


Richard C. Potts, PE
Standard Concrete Products
Deck girder fabrication
Description
Stanley County NCDOT B-3700
 SR 1214 Over Long Creek
 5 Pre-Topped Type III Girders 107’- 4”

Deck girder fabrication
Superstructure Typical Section
Deck girder fabrication
Contract Drawing Beam Detail
Deck girder fabrication
Bed Modification
Deck girder fabrication
Decks Form In Position
Deck girder fabrication
Deck Form Pulled Away
Deck girder fabrication
Deck Forms/Girder Pallet
Deck girder fabrication
Type III Tied
Deck girder fabrication
Type III Cast/ Forms Removed
Deck girder fabrication
Deck Forms In Place
Deck girder fabrication
Shear Key Block Outs
Deck girder fabrication
Deck Steel Bottom Mat Installation
Deck girder fabrication
Deck Steel Complete
Deck girder fabrication
Deck Steel/Barrier Rail Steel
Deck girder fabrication
Embedded Angle
Top Flange Connection
Deck girder fabrication
Poured Deck
Deck girder fabrication
Deck Forms Removed
Deck girder fabrication
Girder Cut Out
Deck girder fabrication
Deck/Girder Joint
Deck girder fabrication
Girder Lifting
Deck girder fabrication
Girder Transport
Deck girder fabrication
Girder Storage
Deck girder fabrication
End View
Deck girder fabrication
Camber 1 1/2 hours After
Detentioning - 3 1/2” - 4”
Deck girder fabrication
Deck View
Deck girder fabrication
Connection Block-out
Deck girder fabrication
Deck Joint

Connection Angle
 Mating Keyway
Deck girder fabrication
Pre-topped Type III Span Setup
Deck girder fabrication
Girder Erection August 18

Erection Began
8:00 AM
 Girders Were Set
In 3.5 Hours With
Rain Showers
Deck girder fabrication
Girder Leveling and
Slope Adjustment

Girders Are Tilted
With Ratchets And
Stabilized With
Wood Blocking
Deck girder fabrication
Metal Diaphragms
Deck girder fabrication
Welded Connection
Deck girder fabrication
Erection Complete August 18
 Time
Frame
. July 5 : Break Ground
(substructure, rip-rap,
temporary access
bridge)
. August 18 : Beams Set
Erection Time 3.5 Hours
. August 24 : Diaphragms and
Shear Keys Complete
Bridge Construction
•Mark H. Foster, Project Manager
•Lee Construction Company of the Carolinas, Inc
Charlotte, North Carolina
Bridge construction
Let: May 17, 2005
Available: June 27, 2005
Complete By: Nov. 1, 2005
Bridge construction
Schedule
Bridge construction
Clearing, Demolition
Bridge construction
Substructure, Temporary Bridge
Bridge construction
Girder Erection
Bridge construction
Girder Erection
Bridge construction
Diaphragm Installation
Bridge construction
Girder Erection
Bridge construction
Shear Key Connection
Bridge construction
Backwall Formwork
Bridge construction
Barrier Rail, Approaches
Bridge construction
Base, Paving, Handrail
Bridge construction
Ready for Traffic

5 October: final
surface.
 13 October:
pavement
markings installed.
 26 October:
punchlist
complete, open for
traffic.
Analysis and Testing
•Janos Gergely, PhD. PE
•The University of North Carolina at Charlotte, Civil
Engineering Department
Analysis and testing
Bridge Details



106’-0” BEARING-TO-BEARING SPAN, INTEGRAL END
WALL
TWO LANE BRIDGE, 30’-0” CLEAR ROADWAY
HL-93 DESIGN LOAD
Analysis and testing
Analytical Study


“LARSA 2000 4th DIMENSION FOR BRIDGES”
SOFTWARE WAS USED TO ESTIMATE THE
FORCES AND STRESSES IN THE CONNECTIONS
AND DIAPHRAGMS
“ANSYS 10.0” WAS USED TO DEVELOP A MORE
REFINED BRIDGE MODEL, WHICH WAS LATER
USED IN A PARAMETRIC STUDY
Analysis and testing
Model Comparison
Stress at Midspan
(Prestress + Dead)
2.50
2.00
1.50
1.00
0.50
0.00
Displacement Comparison
Top of Girder
Bottom of Girder
LARSA™
0.1658
2.8005
ANSYS™
0.1745
2.7890
NCDOT
0.1910
2.7250
*All Values are Com pression
Displacement (in.)
Stress (ksi)
3.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
Deflection Dead ↓
Prestress ↑
Prestress + Dead
↑
LARSA™
1.302
2.980
1.678
ANSYS™
1.235
2.915
1.680
NCDOT
1.300
2.889
1.589
Analysis and testing
FEA Results - Girders
Displacement (in.)
0.1500
Normal Stress (psi)
400.0
300.0
200.0
100.0
0.1000
0.0500
0.0000
0.0
Girder 2
Girder 3
Girder 4
Girder 5
LARSA™
0.0660
0.0720
0.0620
0.0420
102.0
ANSYS™
0.1000
0.1190
0.0890
0.0510
80.0
Load Test
0.0900
0.0500
0.0700
0.0500
Girder 1
Girder 2
Girder 3
Girder 4
Girder 5
LARSA™
143.0
209.0
237.0
203.0
134.0
ANSYS™
130.0
222.0
294.0
195.0
Load Test
70.0
253.0
270.0
118.0
Analysis and testing
FEA Results – Connection Plates
4000
3000
7000
2000
1000
0
Ansys
Load Test
Path 1
Path 2
Path 4
1960.8
2011.4
2188.7
2964
4060
933.8
Comp. Stress Syy (psi)
Tensile Stress Syy (psi)
5000
6000
5000
4000
3000
2000
1000
0
Path 1
Path 2
Path 4
Ansys
4668
4747
4601
Load Test
6307
3602
4744
Analysis and testing
Bridge Load Testing





Instrument types
Instrument Locations
Loading Vehicles
Test Procedure
Testing Types:
- Quasi-static
- Dynamic
Analysis and testing
1E
1W
2E
2W
3E
3W
4E
4W
5E
5W
Test Data
ASD
LRFD
Interior Exterior Interior Exterior Interior Exterior
0.52
0.77
0.58
0.60
0.78
0.26
0.73
0.33
0.75
0.37
1.08
1.16
0.70
0.65
0.69
0.47
0.50
0.95
0.48
0.85
0.67
0.65
0.54
0.74
Distribution
Factors
Analysis and testing
Diaphragm Forces
Analysis and testing
Girder Deformation
Analysis and testing
Impact Factors
DYNAMIC
QUASI-STATIC
Analysis and testing
Connection Evaluation
Analysis and testing
Connection Evaluation
Tension Force
16000
14000
Force (lbs)
12000
Tension #1
10000
Tension #2
8000
Tension #3
6000
Tension #4
4000
2000
0
0
0.2
0.4
0.6
Displacement (in)
0.8
1
Analysis and testing
Connection Evaluation
30000
Shear Force
Force (lbs)
25000
20000
Shear #1
15000
Shear #2
Shear #3
10000
5000
0
0
0.5
1
Displacement (in)
1.5
CONCLUSIONS




ECONOMICAL SHAPE
EASE OF FABRICATION
RAPID CONSTRUCTION
DESIGN ASSUMPTIONS CONFIRMED THROUGH
LOAD TESTING:
– DISTRIBUTION FACTORS
– IMPACT FACTORS
– DEFORMATION AND STRESS LEVELS
– CONNECTION CAPACITY